Usually kitchen hoods are sold without air ducts, pipes for connecting to the ventilation shaft must be purchased separately. Accordingly, you will have to consider various ventilation ducts for hoods and choose the appropriate option. The second task: to outline the route of laying the air channel to acquire the required number of connectors, fittings and fasteners. We will discuss the issues of choosing and installing ventilation ducts in the kitchen in this publication.
Overview of ducts for cooker hoods
To connect the exhaust outlet pipe to the hole of the vertical shaft, 3 types of ducts are used:
- flexible aluminum corrugation of the Aluvent type;
- channels made of plastic PVC round and rectangular cross-section;
- metal boxes of various shapes.
Note. In general, ventilation systems use air ducts from a variety of materials, for example, fabric or three-layer ones with sound insulation. A full overview of ventilation pipes is presented in a separate article.
Now we will analyze separately each group of fume hoods for the kitchen - we list the characteristics, pluses and minuses of the products.
Corrugated Aluminum Pipes
The flexible channel is a soft wire frame covered with thin aluminum foil. A polyester layer is applied on top for better sealing. The pipeline is transported and sold in a compressed state, after unpacking it stretches to the desired length (maximum 5 times).
Duct Specifications:
- wall thickness - up to 100 microns, section - round;
- maximum working temperature - 250 ° C;
- allowable bending radius is 0.7D (D - diameter);
- range of diameters: 80, 100, 110, 120, 125, 130, 140, 150 mm.
The trump card of aluminum sleeves is an affordable price, 1 meter of air duct Ø100 mm in stretched form costs about 50 rubles. (0.9 cu). Thanks to a rich number of sizes, the ventilation duct can be easily selected for the outlet diameter of the exhaust vent and ventilation grill.
The corrugated exhaust duct is quick and easy to install. The pipe is stretched to the required length, one end is put on the fitting of the exhaust unit, the other on the grate. Then the corrugation is fixed with ordinary clamps, this completes the installation.
Note. If the shell is damaged, the sleeve can be cut off and the pipe extended more strongly. But to dock the ends of the 2 corrugations does not work out directly, you will need a hard intermediate pipe.
Disadvantages of flexible channels:
- Appearance of aluminum corrugation does not satisfy modern requirements for interior design. The box is suitable for hoods in the country, in the summer kitchen or apartment with a normal repair. In other cases, the pipe must be hidden behind a decorative casing or plasterboard casing.
- The wavy structure of the walls creates increased resistance to air flow. Fan performance is reduced.
- For the same reason, more body fat is retained within the canal. It is unrealistic to clean the corrugation, it is easier to replace it.
- Aluminum foil is easily damaged by any sharp object.
The last negative point - during operation of the hood, the corrugated pipe is very noisy. The reason is the vibration of thin flexible walls plus a wavy profile that resists air.
Plastic ventilation ducts
For the manufacture of air ducts, polyvinyl chloride (PVC) is used in white. The pipeline does not bend, so the sections of the ventilation network are connected using shaped elements - couplings, nipples, elbows, tees and various adapters. Characteristics of plastic boxes:
- the maximum temperature of the transported medium is 200 degrees;
- sectional shape - round, rectangular (flat);
- diameters of round channels suitable for hoods are 100, 125, 150 mm;
- “Running” sizes of flat baskets - 55x110, 60x112, 60x204, 90x220 mm;
- the length of the standard section is from 35 cm to 2 m.
Reference. Here are the dimensions of the household series pipes. For a fee, you can order the manufacture of non-standard products, for example, a ventilation box Ø180 mm or a square channel 100 x 100 mm. Although only 1-3 meters of air duct will be needed to connect the hood, it is easier to do with the existing dimensions.
Plastic ducts connect to fittings in two ways:
- The round section is worn externally on the counterpart of the mounting element - a branch, tee or nipple.
- Rectangular tubes, in contrast, are inserted inside fittings. Couplings are used to connect straight sections.
In both cases, the joint is carefully sealed with a silicone compound. The cross-sectional shape of the ventilation duct can be changed at any point - install a straight or angular adapter, apply a tee with different conclusions.
The price of plastic is much higher than corrugations of a similar diameter. A meter of Ø100 mm pipe will cost about 180 rubles. (3.15 cu), a rectangular box of equivalent section 110 x 55 mm - 185 rubles. (3.3 c. Here we also need to add the cost of the fittings involved in the scheme.
Other disadvantages of plastic ventilation boxes:
- the color scheme is limited to light shades, it is impossible to find black pipes;
- accordingly, dust and other pollutants are clearly visible on the duct;
- plastic is afraid of overheating above 200 ° C and is able to burn on its own;
- over the years, polyvinyl chloride turns yellow and loses its appearance;
- the walls of the flat ducts bend at the joints, a gap of 1–4 mm wide is formed, as shown in the photo.
Prompt. For high-quality connection of flat channels it is permissible to use short self-tapping screws, which is what the master does in the video (see below). Fasteners tightly tighten the walls of the box and fitting.
We point out the advantages of plastic ventilation systems:
- satisfactory appearance;
- low resistance to air flow due to smooth walls;
- resistance to mechanical and chemical influences;
- low noise during operation of the hood;
- durability, lightweight construction.
Metal channels
For the removal of polluted air from the exhaust into the natural ventilation shaft, 4 types of metal pipelines are used:
- galvanized steel;
- painted metal;
- from stainless steel;
- from copper.
The cross section of the ducts is round, rectangular, square, oval. The choice of sizes is very wide, the connection method is through fittings, like plastic channels.
The main advantage of steel air ducts is aesthetics. Shown in the photo box for extracts from stainless steel or copper will fit into almost any kitchen interior. An exception is galvanized ventilation ducts, whose outer coating quickly becomes cloudy (without loss of anticorrosion properties).
Other advantages of metal boxes:
- durability, long service life;
- low noise level;
- satisfactory wall roughness, low aerodynamic drag;
- metal easily withstands heating up to 500 ° C, does not burn;
- polymer or zinc coating protects surfaces from corrosion.
The main drawback of metal ducts is obvious - the high price. A galvanized channel meter Ø100 will cost at least 180 rubles. e.), but you cannot openly lay it. A similar stainless box costs about 530 rubles / m. paragraph (8.1 cu), not counting the style.
A compromise option is sheet metal products with a colored polymer coating (polyester). Such an air duct is much cheaper than stainless steel and copper.
By weight, ventilation iron boxes lose plastic, but not critical. The thickness of the duct metal is 0.5–0.6 mm, and that of plastic is up to 2 mm; therefore, the difference is not noticeable.
Recommendations for choosing an air duct
A significant selection criterion for homeowners remains the price, aesthetics and operational characteristics of ventilation ducts fade into the background. Here flexible corrugation definitely wins, it is much cheaper than other options, and fittings are not needed.
We will offer our recommendations on how to choose a ventilation duct for your hood:
- 2 types of channels are suitable for external laying - plastic and metal. The first ones are cheaper, but they look worse, it is better to hide them above the cabinets or behind the decorative cladding.
- For a hidden installation, you can take any duct: corrugation, PVC, galvanization. If you are not worried about the noise level, put a cheap aluminum sleeve.
- In a summer house, summer kitchen or porch with a stove, connect the hood with a corrugated pipe. Plastic in such rooms is quickly contaminated, yellowness is quite difficult to remove.
- If an apartment is undergoing expensive repairs, saving and disfiguring the interior is impossible. Match the steel box, fittings and grille to the color of the hood. A stainless steel is perfect for a nickel-plated surface, copper is a golden one.
Tip. There is one way to remove yellowness from white plastic. Try to wipe the stains with a solvent brand 647 or acetone, these chemicals decompose the top layer of plastic. Old deeply ingrained pollution cannot be removed.
Proper connection of the hood
To purchase the required number of pipes and fittings, make a connection diagram of the exhaust outlet of the unit with the ventilation shaft. Follow simple rules:
- Ideally, the total length of the ducts should not exceed 2 m: 1 meter in height + 1 m horizontally to the receiving opening. With a longer length, the performance of the hood will decrease (although the user will not notice the difference, since there is nothing to compare).
- The optimal number of turns 90 ° - two. The more knees, the weaker the “pulls" of the fan due to the increased resistance of the ducts.
- Consider the route of the gasket so that the duct does not intersect with the gas pipe leading to the stove. If intersections cannot be avoided, go around the riser using 45 ° bends rather than right angles.
- If possible, use round channels, in terms of aerodynamics, their throughput is higher. The real plus: less dust is collected on a rounded surface than on a flat one.
- No complex formulas are needed to calculate the diameter or dimensions of a square box. Focus on the cross-sectional area of the exhaust outlet - the air duct should be the same (or more).
- If the total length of the ventilation duct does not exceed 2 m, the cross-sectional area can be reduced by 15% without noticeable deterioration of the unit's performance. But note: a household appliance will become more noisy.
- If the channel length is more than 2 m, it is impossible to reduce the size of the pipe - the hood will significantly lose in power, and it will “wind up” more electricity. And in general, when the stove is located far from ventilation, it is necessary to install a recirculating island hood without any channels.
Since most kitchens have 1 ventilation shaft, when connecting an umbrella, it is important to leave an opening for natural ventilation. That is, the channel is connected to a special flange with a grill, as is done in the photo.
Reference. If the box completely closes the exhaust opening, then the natural air exchange inside the house will stop. The shaft draft will not overcome the resistance of the grease filter of the exhaust hood and fan impeller standing in the air flow path.
The second way to provide ventilation when the hood is not working is to install a tee with a check valve instead of the grill. When the fan is turned on, its damper will slam shut and open again after shutdown. Disadvantage: the valve under the ceiling looks ugly plus collects dust.
The transition from circular to square (and vice versa) is quite acceptable.One condition: the diameter of the duct should not decrease (you can increase). To change the shape of the channel, use the appropriate fittings described below.
In conclusion about the fittings
When installing sections of plastic and steel ducts, a variety of connectors are used. We list these elements and indicate their purpose:
The specified set of parts is quite enough for laying the duct from the hood to the air inlet. The air duct itself is attached to the wall with holders of the appropriate size or laid on top of kitchen cabinets. Each joint must be sealed with silicone sealant.